JP2003053785A - Injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding machine capable of almost linearly moving a punch when the punch is returned to the position in front of an opening after the opening is formed using the punch. SOLUTION: A molten resin material is injected in the molding cavity formed by a mold 15 to perform mold clamping and a gate cutting punch 21 is adapted to the resin material to form the opening. Air pressure or oil pressure is used when the gate cutting punch 21 is moved in the direction opposite to the moving direction at the time of opening after the opening is formed to allow force to act on a piston 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus, and is particularly suitable for being applied to an injection molding apparatus for forming an opening or the like in a molded product.

[0002]

2. Description of the Related Art In recent years, in the field of information recording, various researches and developments regarding optical information recording systems have been advanced. This optical information recording system has an advantage that recording / reproducing can be performed in a non-contact manner and a recording density higher than that of the magnetic recording system by one digit or more can be achieved. Further, this optical information recording system has an additional advantage that it can be applied to each memory type such as a read-only type, a write-once type, and a rewritable type. Therefore, it is considered to be applied to a wide range of applications from industrial use to consumer use as a method that can realize an inexpensive large-capacity file.

Among these, in particular, a digital audio disc (DAD, Digital Audio Disc), an optical video disc, and the like are widely spread as optical discs corresponding to a read-only memory type. The structure of an optical disc such as a digital audio disc will be described below.

That is, the optical disc has a reflection layer made of a metal thin film such as an aluminum (Al) film on one main surface of the optical disc substrate made of a transparent substrate having an uneven pattern such as pits or grooves indicating information signals. A protective film for protecting the reflective layer from moisture (H ₂ O) and oxygen (O ₂ ) in the atmosphere is sequentially provided. When reproducing an information signal in such an optical disc, first, the concavo-convex pattern is irradiated with reproducing light such as laser light from the disc substrate side. Then, the information signal is detected by the difference in reflectance between the incident light of the reproduction light and the return light.

Usually, a disk substrate forming such an optical disk is made of a synthetic resin material and is molded by using a mold device for injection molding. Here, a conventional injection molding apparatus for molding a disk substrate for molding the disk substrate will be described with reference to the drawings.

That is, as shown in FIG. 6, in an injection molding apparatus for molding a disk substrate, a fixed mold 101 fixed to a fixed plate 100a and a movable mold 102 fixed to a fixed plate 100b face each other. The die 10 arranged as
It is configured to have 3. Then, when these fixed mold 101 and movable mold 102 are butted against each other, a molding cavity 104 is formed between the fixed mold 101 and the movable mold 102. The molding cavity 104 has a shape corresponding to the disk substrate 201 to be molded shown in FIG.

An insertion hole is formed at the center of the fixed mold 101 in the injection molding apparatus shown in FIG. A stamper holder support 106 having a substantially annular shape is inserted and provided in the insertion hole.
Further, a sprue bush 107 is provided so as to be fitted into the stamper holder support body 106.

The sprue bush 107 has an annular shape, and a resin injection hole 108 is provided along the central axis of the annular shape. The resin injection hole 108 is configured so that a synthetic resin material such as a melted polycarbonate resin supplied from an injection device (not shown) can flow into the molding cavity 104. That is, the tip end side of the sprue bush 107 is configured so as to face the molding cavity 104. Further, the stamper holder support 106 has a stepped diameter on the front end side facing the molding cavity 104.

The surface of the mold forming the molding cavity 104 of the fixed mold 101, that is, the movable mold 102.
A stamper 109 is attached to the surface portion on the side opposite to. This stamper 109 has a central hole 10 at the center.
It is formed in a disk shape having 9a. The stamper 109 is for forming a concavo-convex pattern corresponding to an information signal or a pre-groove forming a recording track on the disc substrate. The stamper 109 is configured to be supported on the inner peripheral edge of the center hole 109a by the annular stamper inner peripheral holder 110, and also supported on the disc-shaped outer peripheral edge by the annular stamper outer peripheral holder 111. The fixed mold 101 is configured as described above. That is, the stamper inner peripheral holder 110 that supports the peripheral edge of the center hole 109a as the inner peripheral edge side of the stamper 109 is fitted to the outer peripheral side of the stamper holder support body 106, is located on the tip side of the sprue bush 107, and has a fixed metal member. It is attached to the mold 101. A stamper supporting claw portion 110 a is provided on the outer peripheral portion of the stamper inner peripheral holder 110 on the molding cavity 104 side. The stamper supporting claw portion 110 a is for supporting the peripheral edge of the center hole 109 a of the stamper 109.

On the other hand, an insertion hole is also formed at the center of the movable mold 102. A cylindrical sleeve 112 is inserted and provided in the insertion hole of the movable mold 102. This sleeve 112 is used for the molding cavity 10
It is configured to be able to move forward and backward with respect to 4, and is supported by a movable mold. Further, the sleeve 112 is used for the molding cavity 10
The front end face facing 4 is slightly inserted into the movable mold 102. In addition, a cylindrical punch 113 is fitted and provided inside the cylinder of the sleeve 112. The punch 113 has a front end face facing the molding cavity 104 slightly projected from the front end face of the sleeve 112.

The punch 113 is the punch 113.
The cross section perpendicular to the moving direction is circular, and is cylindrical. Further, the shape of the punch 113 on the side surrounded by the fixed platen 100b on the side of the molding machine ejector 114 for pushing out the punch 113 is the molding cavity 104.
It is formed in a stepped shape with a diameter larger than the diameter of a column protruding inward. Further, the punch 113 is used as the molding cavity 104.
A gap is provided between the fixed plate 100b and the surface of the large diameter portion of the punch 113 on the side of the molding cavity 104 so that the punch 113 can move back and forth.

Further, a plurality of springs 115 having the same load are virtually pushed into this gap so that the large diameter (flange) portion of the punch 113 is pushed back uniformly, with a virtual centering on the central axis of the cylindrical shape of the punch 113. The distances from the positions of the vertices of the regular polygon, that is, the center of the central axis of the cylindrical shape of the punch 113 to the respective springs 115 are equal, and the adjacent springs 115 and the punches 11 are arranged.
In the positions where the angles formed by the center of the central axis in the cylindrical shape of 3 are equal to each other, in the direction in which the punch 113 returns to the ejector 114 of the molding machine, between the gap, that is, between the fixed plate 100b and the flange portion of the punch 113. It is provided.

FIG. 7 is a view showing a disk substrate molded by the injection molding apparatus according to this conventional example.

The disk substrate 201 has a punch 1 at the center.
A center hole 201a formed by 13 and a stamper holding groove 202 formed by the stamper supporting claw portion 110a are provided. Further, the information recording area 203a is formed on the main surface of the disk substrate 201 by transferring the mirror image asperities to the stamper 109. The recording surface 2 including the information recording area 203a
03 and the mirror surface 204 on the opposite side are formed. A clamp reference surface 205a, which is a surface to be clamped when a disk is placed on a spindle of a recording / reproducing apparatus (not shown), is formed on the inner peripheral portion of the mirror surface 204. The clamp reference surface 205a is formed by the mirror surface portion of the movable mold 102 during injection molding.

Next, using the substrate injection molding apparatus described above,
A method of forming the disc substrate 201 shown in FIG. 7 will be described.

That is, in FIG. 6, first, the movable mold 102 is butted against the fixed mold 101 to form the molding cavity 104. Then, a molten synthetic resin material such as PC is injected and filled into the molding cavity 104 from the injection device (not shown) through the resin injection hole 108 of the sprue bush 107. At this time, the molten synthetic resin material flows from the central portion toward the outer peripheral side inside the molding cavity 104.

Then, the ejector 114 of the molding machine is pushed out, the punch 113 is projected to the fixed mold 101 side, and the gate is cut to form the center hole 201a in the disc substrate 201 shown in FIG.

FIG. 8 is a diagram showing a conventional disk substrate injection molding apparatus for gate cutting. That is, when the center hole 201a is formed in the disk substrate 201, the punch 11 is pressed by the molding machine ejector 114 with a force stronger than the total load of the spring 115, and further with a force necessary and sufficient to form the center hole 201a.
3 is pushed out toward the sprue bush 107 side. This allows
The synthetic resin material in the extruded portion of the punch 113 is extruded into the resin injection hole 108, and the center hole 201a is formed in the disc substrate 201.

Thereafter, the movable mold 102 is fixed to the fixed mold 101.
By moving it to the side, the mold clamping for compressing the synthetic resin material filled in the molding cavity 104 is performed. Along with this, the synthetic resin material is solidified by cooling. As a result, the disk substrate 201 having a shape corresponding to the molding cavity 104 is formed.

After that, the sleeve 112 is fixed to the fixed mold 101.
The movable mold 102 is fixed to the fixed mold 101 while protruding to the side.
Open the mold to separate from. As a result, the molded disk substrate is released from the mold 103. Then, the pressing of the punch 113 by the molding machine ejector 114 is stopped. Along with this stop, the restoring force of the spring 115 restores the initial state. Then, the disk substrate is separated from the mold. With the above, molding of the disk substrate 201 shown in FIG. 7 is completed.

Although not shown, injection molding for molding a disk substrate is performed in which a punch 113 is returned to the molding machine ejector 114 side after gate cutting by using a gas such as nitrogen or dehumidified clean air instead of a spring at the time of gate cutting. There is also a device. This is because the fixed plate 100b is provided with one or more gas passages so that the gas directly hits the gap between the fixed plate 100b and the punch 113, and a constant pressure is applied to the punch 113 to form the ejector 114 of the molding machine.
It pushes it back to the side.

As described above, the disc substrate 201 shown in FIG. 7 is manufactured, and the disc substrate 201 is used to manufacture an optical disc such as a rewritable optical disc or a read-only optical disc.

[0023]

However, the above-mentioned injection molding apparatus has the following problems. That is, in the method of pushing back the punch by using the restoring force of the spring after forming the center hole on the disc substrate by the punch, when the punch returns, the balance of the punch returning force is bad due to a slight variation in the spring load. The tilt may occur when the punch returns.

Also, in the case of a method in which the compressed gas is directly applied to the flange portion of the punch and the punch is pushed back by the gas pressure, the gas hitting around the gas port becomes strong, and it is difficult to push back the punch with a uniform force. Furthermore, when there is only one gas inlet due to a circuit space problem, etc., tilting may occur during punch return.

As described above, when the punch is tilted at the time of returning, the punch main body and the hole for guiding the sliding of the punch are unevenly contacted with each other, the sliding portion is damaged, and the continuous molding cannot be endured. In the case of, the parts called "caulking" are engaged with each other and do not move at all, and the mold does not function.
In such a state, it becomes impossible to correct the deep scratches and chips left on both parts, and it is necessary to newly manufacture the punch and the part that guides the punch.

In general, when the die maintenance is performed when uneven punching or uneven wear of the punch has occurred, the abrasion portion due to uneven touching or uneven wear is polished by hand with an abrasive. It's fixed. However, the parts that make up these molds are parts with micron tolerance,
There is a problem in that the dimensions change and deform and the balance between the punch and the parts that guide it is lost.

If it is necessary to adjust the strength of punch return during confirmation of operation with the injection molding machine attached or during molding operation, first cool the mold by temperature control (30 to 60). Min), after draining the water in the mold,
Remove the piping and hoses, remove the mold clamp, and lower the mold by using a lifter,
It is necessary to transport the mold to the maintenance room, place it on the surface plate with a crane etc., disassemble it, replace it with a spring with a different spring rate (when using a spring), assemble, etc., and repeat the molding setup from the beginning. Is required, and there is a problem that work time is significantly lost.

Therefore, an object of the present invention is to reduce the inclination of the opening forming means when returning the opening forming means to the position before the opening after forming the opening in the molded product portion by the opening forming means, It is an object of the present invention to provide an injection molding apparatus which improves durability of the apparatus itself, thereby preventing change and deformation of the opening forming means and its peripheral portion and improving the operating rate.

[0029]

In order to achieve the above object, the present invention has a mold capable of forming a cavity and capable of opening and closing, and injecting a material into the cavity formed by the mold. In the injection molding apparatus configured to mold the molded product, the opening forming means configured to form the opening in the molded product and the moving direction of the opening forming means when forming the opening are opposite to each other. And a piston configured to be able to move the opening forming means in this direction.

In the present invention, typically, the molded product has a flat annular shape, and the opening forming means is capable of forming an opening of the flat annular shaped molded product. Further, in the present invention, typically, a flat annular molded article is a disk substrate in an optical recording medium, and an opening can be formed substantially at the center of the disk substrate by the opening forming means.

In the present invention, typically, the opening forming means has a cylindrical shape with a circular cross section perpendicular to the moving direction of the opening forming means. Further, in the present invention, typically, the piston has a cylindrical shape. In the present invention, typically, the central axis of the opening forming means having a cylindrical shape and the central axis of the piston having a cylindrical shape are
It is configured so that they almost match. Further, in the present invention, typically, the piston is composed of a plurality of small pistons, and the plurality of small pistons are respectively located at the positions of the vertices of a regular polygon centered on the central axis of the cylindrical shape of the opening forming means. It is provided.

In the present invention, typically, the piston is movable using compressed gas. Further, in the present invention, typically, the gas is dehumidified clean air or nitrogen gas. Further, in the present invention, typically, the gas can be supplied so as to press one surface of the piston.

According to the injection molding apparatus of the present invention constructed as described above, after the opening is formed in the portion of the molded article by the opening forming means, the direction of movement of the opening forming means when forming the opening is opposite. By returning the opening forming means to the position before opening by using the piston configured to move the opening forming means in this direction, the inclination of the opening forming means at that time can be reduced.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are designated by the same reference numerals.

First, an injection molding apparatus for molding a disk-shaped substrate according to one embodiment of the present invention will be described. Figure 1
1 is a schematic cross-sectional view of an injection molding device for molding a disc-shaped substrate according to an embodiment of the present invention.

As shown in FIG. 1, in the injection molding apparatus for molding a disk-shaped substrate according to this embodiment, a fixed plate 1 is used.
1 and a fixed mold 13 and a movable mold 14 fixed to a fixed platen 13 are arranged to face each other and have a mold 15. Then, when these fixed mold 12 and movable mold 14 are butted against each other, a molding cavity 16 is formed between the fixed mold 12 and the movable mold 14. This molding cavity 16
Has a disk shape, for example, and has a shape corresponding to the molded disk substrate 1 shown in FIG.

Further, in the fixed mold 12 shown in FIG. 1, at the center position of the surface portion on the side forming the molding cavity 16, that is, at the center position of the lower surface portion of the fixed mold 12,
An insertion hole is formed. A sprue bush support ring 12a having a substantially annular shape is inserted and provided in the insertion hole.

The sprue bush support ring 12a in the fixed mold 12 has a shape in which the front end side facing the molding cavity 16 has a stepped diameter. The sprue bush 12b is fitted and provided on the sprue bush support ring 12a.

Further, as shown in FIG. 1, the sprue bush 12b fitted to the sprue bush support ring 12a.
Has a cylindrical shape. Further, the sprue bush 12b is provided with a resin injection hole 12c bored along the central axis of the columnar shape. This resin injection hole 12
Reference character c is for injecting a molten synthetic resin material, for example, a polycarbonate resin, which is supplied from an injection device (not shown), into the molding cavity 16 so as to flow into the molding cavity 16. And this sprue bush 12b is
The tip portion is fixed mold 12 from molding cavity 16
It has a shape that is immersed in the side.

As shown in FIG. 1, a stamper 17 is attached to the lower surface of the fixed mold 12, that is, the surface of the fixed mold 12 facing the movable mold 14. This stamper 17 is
For example, it is for forming a concavo-convex pattern corresponding to an information signal, a pre-groove forming a recording track, and the like. This stamper 17 is made of, for example, nickel (N
i) etc. Further, the stamper 17 is formed in a planar annular shape having a center hole 17a at the center.
Further, a mirror portion having a flat surface is provided in a portion facing the movable mold 14 around the center hole 17a.

The stamper 17 is constructed so that it can be supported on the inner peripheral edge of the center hole 17a by an annular stamper inner peripheral holder 19, and can also be supported on the disc-shaped outer peripheral edge by an annular stamper outer peripheral holder 18. And is attached to the fixed mold 12. That is, the stamper inner peripheral holder 19 that supports the peripheral edge of the center hole 17a as the inner peripheral edge side of the stamper 17 is fitted to the outer peripheral side of the sprue bush support ring 12a and is located on the tip side of the sprue bush 12b. It is attached to the mold 12. A stamper supporting claw portion 19a is provided on the outer peripheral portion of the stamper inner peripheral holder 19 on the molding cavity 16 side.
The stamper supporting claw portion 19 a is for supporting the peripheral edge of the center hole 17 a of the stamper 17.

On the other hand, an insertion hole 14a is also formed at the center of the movable mold 14 perpendicularly to the upper surface of the movable mold 14. That is, this insertion hole 14a is fixed to the fixed mold 12
It is provided at a position facing the front end face of the sprue bush 12b supported by. A sleeve 20 having a cylindrical shape is inserted and arranged in an insertion hole 14a formed in the movable mold 14, and a cylindrical gate cut punch 21 that is fitted in the sleeve 20 is arranged. Has been done. The gate cut punch 21 is supported by the sleeve 20 so as to be movable back and forth with respect to the sleeve 20. Further, the sleeve 20 is supported by the movable mold 14 so as to be movable back and forth with respect to the movable mold 14.
The front end face of the sleeve 20 facing the molding cavity 16 is slightly recessed into the movable mold 14 rather than the upper surface of the movable mold 14. The gate cut punch 21 has a front end face facing the molding cavity 16 slightly projected from the front end face of the sleeve 20.

Further, the gate cut punch 21 is formed in a cylindrical shape having a circular cross section perpendicular to the moving direction of the gate cut punch 21. In addition, a molding machine ejector 2 for pushing out the gate cut punch 21.
The shape of the gate cut punch 21 surrounded by the stationary platen 13 on the second side is formed in a stepped shape having a diameter larger than the diameter of the column protruding to the molding cavity 16 side. Further, a gap is provided between the fixed platen 13 and the surface of the large diameter portion of the gate cut punch 21 on the side of the molding cavity 16 so that the gate cut punch 21 can move forward and backward with respect to the molding cavity 16. Has been.

A plurality of (four in this embodiment) pistons 23 are provided in the gap and the gate cut punch 21 is provided.
Position of the imaginary regular polygon centering on the central axis of the cylindrical shape of the gate cut punch 21, that is, the center of the cylindrical shape of the gate cut punch 21 so as to uniformly push back the large diameter (flange) part of From the center of the axis
The gate cut punches 21 of the molding machine ejector 22 are located at positions where the distances to the respective pistons 23 are equal and the angles formed by the adjacent pistons 23 and the centers of the central axes of the cylindrical shapes of the gate cut punches 21 are equal. It is provided between the fixed platen 13 and the flange portion of the gate cut punch 21 in a direction returning to the direction. The material of the piston 23 is preferably the same as that of the gate cut punch 21 in order to prevent wear and loss of balance, and further, hardening and tempering are performed to strengthen the hardness. It is preferable to set. Further, as a specific material, for example, SUS44
0C etc. are mentioned. Moreover, for example, the pressure applied to each piston 23 can be kept constant by performing simultaneous grinding so that the height of the piston 23 does not vary.

A gas passage 24 is provided so that gas pressure can be applied to these pistons 23.

FIG. 2 is a plan view of an example of a gas path around the gate cut punch 21 of the disk-shaped substrate molding injection molding apparatus according to the above-described embodiment.

First, the movable mold 14 is provided with two gas inlets 27 for taking in gas from the outside of the mold 15. In this embodiment, each gas inlet 2 is centered on the central axis of the columnar shape of the gate cut punch 21.
7 are installed at opposite positions. A gas path 24 is provided from each of the gas inlets 27 toward the center of the gate cut punch 21 in the columnar shape, and a circle whose radius is the distance from the center of the center axis of the gate cut punch 21 to the piston 23 is formed. On the circumference, it is bent into an L shape on the side of the fixed platen 13. An O-ring 25a is provided on the outer periphery of the gas passage 24 in contact with the fixed platen 13, and an O-ring 25b is provided on the inner periphery thereof to prevent gas from leaking in the gas passage 24 between the movable mold 14 and the fixed platen 13. ing.

The stationary platen 13 is formed with an annular gas groove 24a with the exits of the two gas paths 24 of the movable mold 14 bent into an L-shape on the circumference. Also, from this gas groove 24a, the piston 2
It leads to the end face of 3. An O-ring 26 is provided on the outer circumference of the piston 23 to prevent gas from leaking between the stationary platen 13 and the piston 23.

FIG. 3 is a view showing a disk substrate molded by the injection molding apparatus according to this embodiment.

The disk substrate 1 is provided with a center hole 1a formed by a gate cut punch 21 and a stamper holding groove 2 formed by a stamper supporting claw portion 19a at the center. Also, the disk substrate 1
The information recording area 3a is formed by transferring the mirror image asperities to the stamper 17 on one main surface. A recording surface 3 including the information recording area 3a and a mirror surface 4 on the opposite side are formed. A clamp reference surface 5a, which is a surface to be clamped when a disk is placed on a spindle of a recording / reproducing apparatus (not shown), is formed on the inner peripheral portion of the mirror surface 4. This clamp reference surface 5a
Are formed by the mirror surface portion of the movable mold 14 during injection molding.

Next, the disc substrate 1 shown in FIG. 3 is used by using the disc substrate molding die apparatus in the above-described embodiment.
A method of manufacturing the above will be described with reference to the flowchart of forming the disk-shaped substrate shown in FIG.

First, as a pre-preparation for forming a disk substrate by a disk substrate molding die device, a pellet-shaped synthetic resin material such as polycarbonate is supplied to an injection device (not shown) in step S1. Next, in step S2, a plasticizing process is performed to bring the synthetic resin material into a molten state. The temperature of the synthetic resin material at this time is, for example, 32
It is 0 ° C to 370 ° C. Moreover, in the disk substrate molding die device, the molding cavity 16 is formed by abutting the movable die 14 against the fixed die 12.

Then, in step S3, the molten synthetic resin material is injected and filled into the inside of the molding cavity 16 through the resin injection hole 12d of the sprue bush 12b from the injection device (not shown). At this time, the molten synthetic resin material is flown from the central portion toward the outer peripheral side inside the molding cavity 16.

Next, in step S4, the gate cut punch 21 is projected to the fixed mold 12 side, so that FIG.
A center hole 1a is formed in the disc substrate 1 shown in FIG.

The operation of the gate cut punch 21 when forming the center hole 1a in the disc substrate 1 will be described in detail below with reference to FIG.

In this embodiment, pressure is applied to one gas pipe (not shown) by the compressed gas so that the gas is branched into two branches so that the pressures applied to the two gas inlets 27 become the same, and the compressed gas is applied to the gate. Gas groove 24 carved on the circumference around the central axis of the cylindrical shape of the cut punch 21
A constant pressure is constantly applied to the end surface of the piston 23 through a vertical hole formed in the piston 23 through which gas is distributed to each piston 23. Therefore, the gate-cut punch 21 is always acted on by the piston 23 in the direction of the molding machine ejector 22. Examples of the gas used to push back the gate cut punch 21 include nitrogen gas and dehumidified clean air. The pressure applied to the gas pipe is, for example, 3.9.
It is × 10 ⁵ N / m ² (Pa).

That is, the gate cut punch 2 in the normal state
1 is fixed in the position shown in FIG.

Next, FIG. 5 shows a view when the injection molding apparatus of FIG. 1 forms the center hole 1a in the disk substrate 1. As shown in FIG. 5, when forming the center hole 1a in the disc substrate 1, that is, when performing a gate cut, the molding machine ejector 22 makes the center hole 1a in the disc substrate 1 stronger than the total pressure of the piston 23. The gate cut punch 21 is provided with a necessary and sufficient force for forming. As a result, the gate cut punch 21 is moved to the sprue bush 12b side, the synthetic resin material in the center hole 1a portion is extruded into the resin injection hole 12d, and the center hole 1a is formed and shaped.

Next, in step S5, the movable mold 1
By moving 4 to the fixed mold 12, the mold is clamped to compress the synthetic resin material filled in the molding cavity 16, and the synthetic resin material is shaped. The temperature of the mold 15 at this time is, for example, 125 ° C. to 130 ° C. The mold clamping pressure is 20 tons, for example.

Then, a pressure holding process is performed in step S6, and subsequently, cooling is performed in step S7 to solidify (shrink) the synthetic resin material. As a result, the disk substrate 1 corresponding to the molding cavity 16 is formed.

Thereafter, in step S8, the mold opening is performed in which the movable mold 14 is separated from the fixed mold 12 while the sleeve 20 is projected toward the fixed mold 12. As a result, the molded disk substrate 1 is released from the mold 15. Then, the gate cut punch 21 is formed by the molding machine ejector 22.
, And the gate cut punch 21 returns to the original position in FIG. 1 by the uniform and smooth return force of the piston. Then, the disk substrate 1, which is this molded product, is separated from the fixed mold 12 to complete the molding of the disk-shaped substrate.

As described above, according to this embodiment, the gate cut punch 2 is used by the molding machine ejector 22.
1 is pushed to the side of the sprue bush 12b to form the center hole 1a of the disc substrate 1 and then returns the gate cut punch 21 to the position before the formation of the center hole 1a.
From the gas inlet 27 at a certain position through the annular gas groove 24a engraved on the fixed plate 13, and further to each piston 2
By applying uniform gas pressure from the two gas inlets 27 to the gas path 24 that reaches the piston 23 through the vertical hole leading to 3, the pressure applied to each piston 23 is kept constant, which results in accurate and smooth operation. The return operation of the gate cut punch 21 is performed.

Further, when the disc substrate 1 is taken out by the robot arm after the gate cut punch 21 is ejected, the return of the gate cut punch 21 is sure and smooth, and therefore the disc substrate 1 take-out defect is reduced. A stable molding cycle can be maintained.

Further, since the gate cut punch 21 and the piston 23 are always in contact with each other and can be considered as an integrated part, there is no sense of incongruity such as adding a new part, like the conventional mold. It can be handled.

Furthermore, since there is little resistance when the gate cut punch 21 returns, the gate cut punch 21 can be returned with a pressure smaller than the punch return force of the conventional die. Therefore, even if an abnormality such as galling occurs in the sliding portion of the component, the gate cut punch 21 does not try to return forcibly, so that damage to the component can be suppressed more than in the conventional injection molding apparatus.

The embodiments of the present invention have been specifically described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made based on the technical idea of the present invention.

For example, the injection molding apparatus according to the embodiment of the present invention described above is an injection molding apparatus for molding a disk substrate for a hard disk (HD), an optical hard disk (OH).
D) disk substrate injection molding machine, compact disc (CD), write-once compact disc (CD-R, Compact Disc Recordable), rewritable compact disc (CD-RW, Compact Disc ReWri)
table), DVD (Digital Versatile Disc), write-once DVD (DVD-R, Digital Versatile DiscRecordab)
le), DVD-RW (Digital Versatile Disc-ReWri
table), DVD + RW (Digital Versatile Disc + R)
eWritable), DVR (Digital VideoRecording syste
m), MO (Magnetic Optical Disc), MD (Mini Dis)
It can be applied to an injection molding device for molding a disk substrate for optical disks such as c).

For example, the numerical values, disk substrate materials and the like mentioned in the above embodiment are merely examples, and different numerical values and disk substrate materials may be used if necessary.

For example, in the above-mentioned embodiments, a polycarbonate resin is used as the material of the disk substrate, but a low water-absorbing resin such as cycloolefin polymer (for example, Zeonex (registered trademark)) is used in addition to polycarbonate. It is also possible.

Further, for example, in the above-described embodiment, the gas inlet 27 and the gas passage 24 are arranged in the fixed plate 13 and the movable mold 14, but these passages are provided only in the fixed plate 13. It is also possible to provide it at other places, and further, it is possible to change the handling shape from the gas inlet 27 to the gas groove 24a, or to make the gas groove 24a tubular.

Further, for example, in the above-described embodiment, the number of pistons 23 is four, but the number is not limited to four. Considering the balance, three are considered to be good, but considering the gas path, the number of pistons 23 is preferably even, rather than odd, and thus four is optimal. Further, the number of gas passages 24 is not limited to two, and it is preferable that the number of pistons 23 is even, as in the case of the number of pistons 23.

Further, for example, in the above-described embodiment, the piston 23 is shaped like a coma, but if there is enough space for the gas passage 24, one ring-shaped piston is used as the gate cut punch 21. It can also be used at the center of. At that time, the O-shaped groove is inserted into the outer circumference of the ring-shaped piston and the inner circumference of the groove into which the ring-shaped piston of the mold is inserted.
By inserting the ring, a drive similar to the above-described embodiment can be obtained.

Further, for example, in the above-described embodiment, the compressed nitrogen pressure is used to apply the pressure to the piston 23, but it is also possible to apply the pressure using another gas or liquid. However, if the pressure is changed to hydraulic pressure, the size of the device becomes large, and even if all the parts used in the clean room are degreased with an ultrasonic cleaner, the use of hydraulic pressure purposely disassembles the device. Since it becomes difficult to keep the device clean, for example, when it becomes covered with oil, it is optimal to use gas pressure.

[0074]

As described above, according to the present invention, when the opening forming means of the injection molding apparatus forms an opening in the portion of the molded product and then the opening forming means returns to the position before the opening, the opening forming means is formed. Since the inclination of the means can be reduced, the durability of the injection molding apparatus itself is improved, thereby preventing the opening forming means of the injection molding apparatus and its peripheral portion from being changed or deformed, and the operating rate of the injection molding apparatus. Also improves.

[Brief description of drawings]

FIG. 1 is a sectional view showing an outline of an injection molding apparatus for molding a disk-shaped substrate according to an embodiment of the present invention.

FIG. 2 is a plan view schematically showing an air path of the injection molding device for molding a disc-shaped substrate according to the embodiment of the present invention.

FIG. 3 is a sectional view showing a disk substrate molded by the disk-shaped substrate molding injection molding apparatus according to the embodiment of the present invention.

FIG. 4 is an example of a flow chart of forming a disk substrate by an injection molding apparatus.

FIG. 5 is a cross-sectional view schematically showing a disc-shaped substrate molding injection molding apparatus according to an embodiment of the present invention when a gate is cut.

FIG. 6 is a cross-sectional view schematically showing an injection molding device for molding a disk-shaped substrate according to a conventional example.

FIG. 7 is a cross-sectional view showing a disk substrate molded by an injection molding device for molding a disk-shaped substrate according to a conventional example.

FIG. 8 is a cross-sectional view showing an outline of gate cutting of an injection molding device for molding a disk-shaped substrate according to a conventional example.

[Explanation of symbols]

1 ... Disk substrate, 1a ... Center hole, 1
1, 13 ... Fixed plate, 12 ... Fixed mold, 12a
..Spruch bush support ring, 12b ... Sprue bush, 12c ... Resin injection hole, 12d ... Bottom surface, 14
... Movable mold, 14a ... Insertion hole, 14b ... Upper surface, 15 ... Mold, 16 ... Molding cavity, 1
7 ... Stamper, 17a ... Center hole, 18 ...
Stamper outer peripheral holder, 19 ... Stamper inner peripheral holder, 19a ... Stamper supporting claws, 20 ...
・ Sleeve, 21 ・ ・ ・ Gate cut punch, 21a ・
..Gate cut punch tip portion, 21b ... Gate cut punch flange portion, 22 ... Molding machine ejector, 23 ... Piston, 24 ... Gas path, 24a
... Gas groove, 25a, 25b, 26 ... O-ring,
27 ... Gas inlet

Claims (10)

[Claims] 1. An injection molding apparatus having a mold capable of forming a cavity and having an openable / closable mold, wherein a material is injected into the cavity formed by the mold to mold a molded product. An opening forming means capable of forming an opening in a portion of the molded product, and the opening forming means movable in a direction opposite to a moving direction of the opening forming means when forming the opening. An injection molding apparatus comprising: a configured piston. 2. The molding according to claim 1, wherein the molding has a plane annular shape, and the opening forming means is capable of forming an opening of the plane annular molding. Injection molding equipment. 3. The flat ring-shaped molded product is a disk substrate in an optical recording medium, and the opening can be formed substantially at the center of the disk substrate by the opening forming means. The injection molding apparatus according to claim 2. 4. The injection molding apparatus according to claim 1, wherein the opening forming means has a columnar shape having a circular cross section perpendicular to the moving direction of the opening forming means. 5. The injection molding apparatus according to claim 4, wherein the piston has a cylindrical shape. 6. The structure according to claim 5, wherein a central axis of the opening forming means having the cylindrical shape and a central axis of the piston having the cylindrical shape are substantially aligned with each other. Injection molding equipment. 7. The piston is composed of a plurality of small pistons, and the plurality of small pistons are provided at respective apexes of a regular polygon centered on a central axis of a cylindrical shape of the opening forming means. The injection molding apparatus according to claim 4, wherein: 8. The injection molding apparatus according to claim 1, wherein the piston is configured to be movable by using compressed gas. 9. The injection molding apparatus according to claim 8, wherein the gas is dehumidified clean air or nitrogen gas. 10. The injection molding apparatus according to claim 8, wherein the gas can be supplied so as to press one surface of the piston.